1. Field of the Invention
The present invention relates to a method of using an electric arc gasifier to process waste. A plasmatic primary fluid heated by an electric arc mixes with injected waste to crack and gasify the components of the mixture. The instant method provides a high waste destructive rate with a low cost process, which can be aimed to produce chemical or gaseous products and recover high value metals.
2. Description of the Related Art
There are a number of methods developed to process waste in various forms, and with a variable degree of efficiency as the economics of most processes do not account for a high degree of destruction of the waste, i.e. low cost processes creates a liability from an environmental point of view. On the other hand, processes that do have high destruction rates also have very expensive operating costs. Our invention overcomes these problems to combine low operating and capital costs with high destruction efficiency.
Common methods include the use of electrodes to implement the use of high temperatures in a furnace for destroying waste (Queiser et al). Also, known in the art are methods and apparatuses for disintegrating or incinerating waste using arc-forming electrodes. Electric arcs abruptly raise temperatures of compounds from the heat of alternative fluids to form a high temperature plasma. In particular, as can be seen in U.S. Pat. No. 5,811,752 by Titus et al., a molten pool provides a conducting path for at least two arc forming electrodes capable of providing and maintaining joule heating to convert waste dissolved in a liquid pool to stable products. Operating conditions of this process are dependent, however, on the desired liquid pool medium used for chemical modification of the waste. Gaseous or liquid compounds, and even solids with high volatile content may bypass the destruction medium as they fall into the port of melted down ceramic metal, thereby producing secondary waste.
As can be demonstrated by U.S. patent application Ser. No. 09/152,636, an electric arc-activated, non-catalytic burner can produce synthetic gas by mixing an injection with an ignited primary fluid under high temperature and high pressure to produce gases used for combustion or other industrial processes. A new method of use can be demonstrated to account for waste processing of products that have variable chemistry.
As an example, electric arc furnaces are used for the production of steel, and the material charged to these furnaces is usually steel scrap and eventually direct reduced iron. The production of steel by this method generates a significant amount of dust that is collected in a baghouse or similar equipment in the fumes purification system. The disposal of EAF dust is costly because of the presence of heavy metals in its chemistry. The present method is particularly suitable for the treatment and recycling of the components of this dust, as well as other costly and inefficiently recoverable wastes, such as chlorinated hydrocarbons.
Chlorinated hydrocarbons are a waste produced by some chemical processes. The disposal of this waste is costly and the recovery is inefficient. The electric arc gasifier can process these chlorinated hydrocarbons, recover hydrochloric acid, and produce synthetic gas (CO, H.sub.2, or carbon dust and H.sub.2) in a very efficient manner.
The bulk of chlorinated hydrocarbons is processed in incinerators (rotary kilns). The thermal efficiency of the incinerators is low. The capital cost is in the same order of the electric arc gasifier process or higher, but the operating cost is higher due to low efficiency and consumable cost. In addition, environmental permitting is difficult because of formation of dioxins and NOx. The emissions also increase the liability associated to the operation of the plant.
There is a need, then, for a more efficient method of processing waste using the electric arc method that will automatically correct operating conditions based on the complexity of waste products and variably be capable of recycling desired compounds.